There are surgical procedures that employ a laser to vaporize a portion of tissue. For example, a Carbon Dioxide (CO.sub.2) or Argon Ion laser is used to perform a myringotomy, wherein a 1 mm diameter hole is made in an ear drum. To accomplish this, a surgeon focuses the laser optics to provide a 1 mm spot size. The laser is then energized for a period of 50 to 100 msec, emitting a pulse of laser light that vaporizes the ear drum tissue upon contact, leaving a 1 mm hole. The vaporization of the tissue is believed to cause an acoustic shock wave in the ear drum that is perceived by the patient as an abrupt, loud noise, described as a "pop" sound. Children most likely perceive the noise as painful and disturbing, and are often reluctant to submit to the procedure again. Furthermore, since the intensity of the laser spot is typically described by a Gaussian distribution, only the central portion of the spot has an intensity sufficient to vaporize tissue. The outer skirt of the spot induces tissue charring and coagulation, which can be undesirable side-effects of current techniques.
The stapes is the smallest of three small bones that together transmit sound from the ear drum and ultimately to the auditory nerve. Normally, the stapes presses against the vestibular window. If the stapes should become fixed to the vestibular window such that sound cannot be effectively transmitted, then impaired hearing results. To remedy this, a small hole is made in the stapes. A prosthetic device is inserted in the hole such that the prosthetic device extends toward and contacts the vestibular window. Thus, sound can again be effectively transmitted. One current technique for making the small hole is to form a circular array of closely spaced, yet smaller holes, and then remove the circular region surrounded by the smaller holes. The prosthetic device is then inserted in the now-vacant region. However, it is difficult and time-consuming for a surgeon to precisely position the laser beam and fire the laser to produce the circular array of smaller holes. Due to lack of precision, the shape of the circular region may not closely conform to the shape of the prosthesis, resulting in poor contact of the prosthetic device with the vestibular window, thereby creating a possibility of perilymph leakage and dislodging of the prosthetic device, resulting in renewed hearing impairment.